I. Field of the Invention
The present invention relates generally to windshield wiping systems and, more particularly, to a windshield wiping system utilizing heated windshield washing fluid.
II. Description of the Prior Art
In a typical windshield wiper system of the type used in automotive vehicles, the windshield wiper fluid is pumped from a reservoir of washing fluid to one or more nozzles having their output directed onto the windshield. In some cases, the nozzles themselves are carried by the wiper arms which carry the wiper blade or even alternatively by the blades themselves.
A disadvantage of these previously known wiper systems is that, in cold climates, ice accumulation on the windshield, wiper blades and nozzle openings is a common occurrence making driving hazardous and unpleasant due to the resulting poor visibility through the windshield. Such ice accumulation forms over a period of time so that the washer fluid in the reservoir approaches the cold outside ambient temperature. Consequently, since the washer fluid itself is at a very cold temperature, it is not possible to effectively melt the ice on the nozzles, blades and windshield by using only the wiper fluid. Instead, the ice must be manually scraped from the windshield and knocked off the wiper blades, and in the case of frozen nozzles, the washer/wiper system can be rendered useless for a period of time amounting to days.
There have, however, been previously known windshield wiper systems utilizing heated washer fluid. These previously known systems utilize engine heat or alternatively an electrical heater to heat the windshield washing fluid. The heated washing fluid is then used to melt the ice from the windshield.
These previously known windshield wiping systems utilizing heated washing fluid, however, have not proven satisfactory in operation and have not achieved acceptance in the industry for reasons generally including excessive cost and complexity, inadequate heating, nozzle freeze up and ineffective delivery to critical locations needing deicing.
More specifically, one reason that the previously known heated windshield wiper systems which employ engine heat to heat the washing fluid have not proven satisfactory is that the washer fluid delivered to the windshield was ineffectively heated. When this happened, the windshield washing fluid, being only moderately heated, only marginally facilitated the melting of the ice from the vehicle windshield and further resulted in using too much fluid thus, the limited capacity reservoir was quickly emptied.
The previously known windshield wiping systems utilizing electric heaters have likewise not proven satisfactory in operation. One disadvantage of these previously known systems is that the heating element did not effectively heat the windshield washing fluid so that the resulting moderately heated washing fluid only moderately facilitated the melting of the ice from the windshield and again, excessive fluid was used quickly emptying the reservoir. Attempts to use higher output heating elements have resulted in failed heating elements, boiling and purging of the washing fluid with its depressed boiling point from alcohol, and other undesirable operating characteristics.
A still further disadvantage of these previously known systems is that the ice accumulation occurs not only on the windshield but also upon the flexible bridging frame that supports the rubber wiping element. When this occurs, the frame cannot flex in its normal fashion in order to maintain the wiper blade in contact with the windshield throughout the stroke of the wiper arm. This results in non-cleaning of the windshield which continues until the bridging frame flex joints for the wiper blade are free of ice.
Lack of very uniform distribution and melt time of the heated fluid on the critical vision area of the windshield before being swept off has limited effectiveness of previously known systems.
Short clean wiping life has universally been a problem with previously known wiper blades.